1. Field
The present disclosure relates to apparatus and methods for timing recovery in a timing tracking circuit in a wireless communication transceiver and, more particularly, to apparatus and methods for determining when a timing tracking circuit is incorrectly tracking timing of a wireless signal received by the transceiver and resetting the timing tracking circuit in order to mitigate degradation of the quality of a signal output by the transceiver.
2. Background
In certain wireless communications systems, such as those employing orthogonal frequency division multiplexing (OFDM), timing tracking of wireless communications signals is important for maintaining the quality of audio and visual signal information contained in those signals. In systems, such as OFDM, timing tracking circuits within transceivers of such systems get locked to the incorrect timing window. For example, OFDM frames typically include 1,024 chips. Thus, when the timing tracking circuit is locked to a wrong timing window or frame, the timing will be in entire 1,024 chips of the correct timing window. When this happens, the timing circuit is not able to recover and will fail to decode any packets subsequently received, which results in degradation of the radio and/or audio quality of the receiver.
It is further noted that in communications systems such as OFDM systems, frames of information are arranged into what are termed “superframes” that contain a number of smaller frames each containing a number of packets containing communications data including video and audio data. Additionally in such communications systems, each frame includes time division multiplexed (TDM) pilot channels that are used for channel estimation and also at initial acquisition of a signal to establish the timing tracking. Typically in some systems, the TDM pilot signals are channels that are only acquired at the initial acquisition of the signal and are not used subsequently for setting the timing tracking until the transceiver enters another initialization mode, such as after a transceiver has awakened from a. sleep mode. In such systems, however, when timing tracking is locked to the wrong timing window, as discussed above, the quality of the coded information is degraded.